颗粒材料的微观临界状态理论模型

存在临界状态是颗粒材料的一个重要特性。基于孔隙胞元的颗粒离散元方法对二维颗粒体进行双轴加载数值试验，在详细分析数值模拟结果的基础上，从微观几何组构的角度揭示了临界状态的存在机制。基于剪胀性原理，提出了以接触价键表征的微观临界状态理论模型，得到了接触价键与塑性剪切应变的关系表达式，理论模型的结果和二维离散元数值模拟得到的结果吻合较好。通过比较不同情况下数值结果和理论模型中的参数，得到以下结论：表征微观临界状态的参数（临界接触价键和达到临界状态所需要的塑性剪切应变）依赖于颗粒体的微观特性，如颗粒形状、表面摩擦性质、颗粒体的围压和初始孔隙比。

Microscopic theoretical model of critical state for granular materials

Critical state is an important phenomenon exhibited in granular materials. Numerical simulations of two-dimensional particulate arrays are carried out using granular discrete element method based on void cells. The numerical simulation results are analyzed in detail to reveal the critical state from the viewpoint of microscopic geometric fabric. Based on the dilatancy of granular materials the micromechanical theoretical model of critical state in terms of valence is proposed. An implicit relationship between valence and plastic shear strain is obtained. The solution of the theoretical model confirms well with the numerical results. The important conclusion is drawn as follows: the parameters related to the microscopic theoretical model, including the critical valence and the plastic shear strain corresponding to critical state, are dependent on the microscopic properties such as the particle shape, surface friction, the consolidation stress and the initial void ratio of the granular assembly.